Astronomers have been around for as long as humanity has pondered about the skies above us. Since antiquity, we have looked to it for some semblance of regularity in our lives; our notion of months, years, and seasons have long been tied to the patterns of shining objects that we see above us. Certainly, we are far better-equipped now than the astronomers of yore were thousands of years ago; yet here we are, looking at the very same sky.
It’s interesting to note that just like our modern astronomers now, the astronomers of antiquity were also recording accounts of what they saw up there back then. As there was no advanced imaging equipment at the time to lock these cosmic events in place as pictures, these olden stargazers had to resort to what recording equipment was available to them at the time: a notebook and something to write with.
From there, everything else was fair game. Given the lack of advanced telescopes and imaging equipment, bright points in the sky were often called “stars,” whether it actually be a star or something else, like a supernova. This was certainly the case in the year 1181, when astronomers recorded what they called the “Guest Star.”
First documented by Japanese and Chinese astronomers at the time, the “Guest Star” was a bright point in the sky that lasted for 185 days, from the 6th of August 1181 to the 6th of February 1182. These astronomers also recorded where it was in the sky at the time. This would prove crucial to the astronomers of today, who believe they had successfully identified the light source of this historical “star,” which is officially the supernova SN 1181. Their findings can be found published in the Astrophysical Journal Letters.
In the study, they targeted a specific nebula called Pa 30, which sat at roughly the same area as the “Guest Star” which was spotted nearly 900 years before. Using specialized equipment, they identified the rate of expansion of the nebula to be about 1,100 km/s (684 mi/s); this means that given the measured size of the nebula, these scientists were able to pinpoint when the Pa 30 nebula exploded: roughly 900 years ago, coinciding with the appearance of the “Guest Star.”
Additionally, Pa 30 had been proposed to be part of a system resulting from the merging of two white dwarfs before. The other component of the system is a star designated IRAS 00500+6713, better known as Parker’s star. Both Pa 30 and Parker’s star were believed to have emerged from this white dwarf merger, causing the appearance of SN 1181 which took place some 900 years ago. The white flash in the sky persisted for some 180 days after it appeared, which ancient Japanese and Chinese astronomers recorded as the “Guest Star.”
“Combining all this information such as the age, location, event brightness and historically recorded 185-day duration, indicates that Parker’s star and Pa 30 are the counterparts of SN 1181,” according to University of Manchester professor Albert Zijistra.
He added: “The remnant is crucial for identifying the type of supernova, while the known time of the explosion and duration constrain the models of the evolution of the remnant. […] The historical reports place the guest star between two Chinese constellations, Chuanshe and Huagai. [Parker’s star] fits the position well. […] That means both the age and location fit with the events of 1181.”
Supernovae resulting from the merger of two white dwarfs are thought to be rare, and are officially called Type Iax supernovae. Zijistra noted that only about 10% of all known supernovae fit this type, leading to several questions regarding their true nature. The fact that both the supernova remnant and the resulting merged star of SN 1181 were both identified means that “[SN 1181] is the only such event where we can study both the remnant nebula and the merged star, and also have a description of the explosion itself,” according to Zijistra.
To Zijistra, “[SN 1181] is the only Type Iax supernova where detailed studies of the remnant star and nebula are possible. It is nice to be able to solve both a historical and an astronomical mystery.”
SN 1181 is one of only nine supernovae within the Milky Way Galaxy that had been recorded in historical texts. Of these nine, only five have been identified—meaning SN 1181 now sits as the sixth identified historical supernova.
(To find out more about supernovae and their role in creating the elements of the universe, check out our piece about two astronomers who played with the idea using colored markers and a periodic table. Additionally, here’s another piece about a particular supernova that appeared in three spots in the sky all at once.)
References
- Carter, J. (2021, September 15). A supernova that stunned stargazers in the year 1181 has finally been found—And it’s a ‘zombie’ star. Forbes. https://www.forbes.com/sites/jamiecartereurope/2021/09/15/a-zombie-supernova-that-stunned-stargazers-in-the-year-1181-has-finally-been-found-welcome-to-parkers-star/
- Jha, S. W. (2017). Type iax supernovae. ArXiv:1707.01110 [Astro-Ph], 375–401. https://doi.org/10.1007/978-3-319-21846-5_42
- Ritter, A., Parker, Q. A., Lykou, F., Zijlstra, A. A., Guerrero, M. A., & Le Dû, P. (2021). The remnant and origin of the historical supernova 1181 ad. The Astrophysical Journal Letters, 918(2), L33. https://doi.org/10.3847/2041-8213/ac2253
- Saplakoglu, Y. (2021, September 17). Nearly 900 years ago, astronomers spotted a strange, bright light in the sky. We finally know what caused it. Livescience.Com. https://www.livescience.com/cosmic-mystery-ancient-china-supernova
- Sci-News. (2021, September 20). Astronomers Identify Remnant of Historical Supernova SN 1181. Sci-News. http://www.sci-news.com/astronomy/supernova-remnant-sn-1181-10083.html
